Piperidine derivatives

ABSTRACT

Novel Compounds of the formula: ##STR1## [wherein A is an α-amino acid residue; B is a group represented by the formula: ##STR2## (wherein R 4  is hydrogen, lower alkyl, aralkyl or amino-lower alkyl), whereby the linkage between the symbols A and B designates a peptide bond and the group R 4  is B may be linked with A; R 1  is hydrogen, lower alkyl or aralkyl; R 2  is hydrogen, lower alkyl, aralkyl or acyl; X is alkylene] and salts thereof posses, for example, inhibitory activity on angiotension converting enzyme, and are useful as an agent for diagnosis, prevention or treatment of hypertension as well as circulatory diseases such as cardiopathy and cerebral apoplexy.

This application is a division of Ser. No. 806,810, filed Dec. 10, 1985.

TECHNICAL FIELD

This invention relates to novel piperidine derivatives which are ofvalue as a pharmaceutical.

BACKGROUND ART

Although there have been known various compounds exhibiting inhibitoryactivity on angiotensin converting enzyme, any compound with suchactivity having a moiety of ω-(4-piperidyl)-α-amino acid has not beenknown at all.

The present inventors, after intensive search for the compound whichexhibits inhibitory activity on angiotensin converting enzyme and isuseful as a therapeutic agent for hypertension and circulatory diseases,such as cardiopathy and cerebral apoplexy, succeeded in producing thepiperidine derivatives exhibiting excellent actions, and have completedthis invention.

DISCLOSURE OF THE INVENTION

This invention provides compounds of the formula: ##STR3## [wherein A isan α-amino acid residue; B is a group represented by the formula:##STR4## (wherein R⁴ is hydrogen, lower alkyl, aralkyl or amino-loweralkyl), whereby the linkage between the symbols A and B designates apeptide bond and the group R⁴ in B may be linked with A; R¹ is hydrogen,lower alkyl or aralkyl; R² is hydrogen, lower alkyl, aralkyl or acyl; Xis alkylene] and salts thereof.

In the above formulae, the α-amino acid residue as represented by Aincludes, for example, chain α-amino acid residues, such as alanino,N.sup.α -arginino, N.sup.α -asparagino, glycino, N.sup.α -histidino,leucino, N.sup.α -lysino, cysteino, tryptophano, thyrosino and valino;α-amino acid residues which constitute such chain α-amino acid residueshaving their carboxyl groups esterified; and groups represented by theformulae: ##STR5## wherein R³ is hydrogen, lower alkyl or aralkyl.

The group which the group R⁴ in B combines with A to form includes, forexample, groups as represented by the formulae: ##STR6## [wherein R³ ishydrogen, lower alkyl or aralkyl].

The esterified carboxyl group contained in the above chain α-amino acidresidues includes, for example, lower-(C₁₋₄)-alkoxycarbonyl andaralkyloxycarbonyl, such as phenyl-lower-(C₁₋₄)-alkoxycarbonyl.

With reference to the above formula (I), the lower alkyl grouprepresented by R¹, R², R³ or R⁴ includes alkyl groups of about 1 to 4carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl,sec-butyl and tert-butyl. The aralkyl group represented by R¹, R², R³ orR⁴ includes phenyl-lower(C₁₋₄)-alkyl groups, such as benzyl, phenethyl,3-phenylpropyl, α-methylbenzyl, α-ethylbenzyl, α-methylphenethyl,β-methylphenethyl and β-ethylphenethyl.

The acyl group represented by R² includes lower-(C₁₋₅)-alkanoyl (e.g.,acetyl, propionyl), benzoyl, phenyl-lower-(C₁₋₄)-alkoxycarbonyl (e.g.,benzyloxycarbonyl) and lower-(C₁₋₄)-alkoxycarbonyl (e.g.,tert-butoxycarbonyl) groups.

The amino-lower alkyl group represented by R⁴ includes amino-lower alkylgroups of about 1 to 4 carbon atoms, such as aminoethyl, aminopropyl andaminobutyl.

The alkylene chain represented by X includes, for example,straight-chain or branched-chain alkylene chains of about 1 to 7 carbonatoms, being exemplified by divalent groups, such as methylene,ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene,heptamethylene, propylene, ethylmethylene and dimethyltetramethylene.The said alkylene bridges may have in the chain an unsaturated bond orunsaturated bonds (e.g., double bond, triple bond).

Specific disclosure of compounds of this invention includes, forexample, the compounds as shown in Tables 1 to 5.

                                      TABLE 1                                     __________________________________________________________________________     ##STR7##                                                                     A                 B         X      R.sup.1                                                                          R.sup.2                                 __________________________________________________________________________     ##STR8##                                                                                        ##STR9## (CH.sub.2).sub.4                                                                     H  H                                        ##STR10##                                                                                       ##STR11##                                                                              (CH.sub.2).sub.4                                                                     C.sub.2 H.sub.5                                                                  H                                        ##STR12##                                                                                       ##STR13##                                                                              (CH.sub.2).sub.4                                                                     C.sub.2 H.sub.5                                                                  COOCH.sub.2 Ph                           ##STR14##                                                                                       ##STR15##                                                                              (CH.sub.2).sub.4                                                                     H  H                                        ##STR16##                                                                                       ##STR17##                                                                              (CH.sub.2).sub.4                                                                     C.sub.2 H.sub.5                                                                  H                                        ##STR18##                                                                                       ##STR19##                                                                              (CH.sub.2).sub.4                                                                     C.sub.2 H.sub.5                                                                  COOCH.sub.2 Ph                           ##STR20##                                                                                       ##STR21##                                                                              (CH.sub.2).sub.4                                                                     H  H                                        ##STR22##                                                                                       ##STR23##                                                                              (CH.sub.2).sub.4                                                                     C.sub.2 H.sub.5                                                                  H                                        ##STR24##                                                                                       ##STR25##                                                                              (CH.sub.2).sub.4                                                                     C.sub. 2 H.sub.5                                                                 COOCH.sub.2 Ph                           ##STR26##                                                                                       ##STR27##                                                                              (CH.sub.2).sub.4                                                                     H  H                                        ##STR28##                                                                                       ##STR29##                                                                              (CH.sub.2).sub.4                                                                     C.sub.2 H.sub.5                                                                  H                                        ##STR30##                                                                                       ##STR31##                                                                              (CH.sub.2).sub.4                                                                     C.sub.2 H.sub.5                                                                  COOCH.sub.2 Ph                           ##STR32##                                                                                       ##STR33##                                                                              (CH.sub.2).sub.4                                                                     H  H                                        ##STR34##                                                                                       ##STR35##                                                                              (CH.sub.2).sub.4                                                                     C.sub.2 H.sub.5                                                                  H                                        ##STR36##                                                                                       ##STR37##                                                                              (CH.sub.2).sub.4                                                                     H  H                                        ##STR38##                                                                                       ##STR39##                                                                              (CH.sub.2).sub.4                                                                     C.sub.2 H.sub.5                                                                  H                                        ##STR40##                                                                                       ##STR41##                                                                              (CH.sub.2).sub.4                                                                     H  H                                        ##STR42##                                                                                       ##STR43##                                                                              (CH.sub.2).sub.4                                                                     C.sub.2 H.sub.5                                                                  H                                        ##STR44##                                                                                       ##STR45##                                                                              (CH.sub.2).sub.3                                                                     H  H                                        ##STR46##                                                                                       ##STR47##                                                                              (CH.sub.2).sub.5                                                                     H  H                                        ##STR48##                                                                                       ##STR49##                                                                              (CH.sub.2).sub.3                                                                     H  H                                        ##STR50##                                                                                       ##STR51##                                                                              (CH.sub.2).sub.5                                                                     H  H                                       __________________________________________________________________________

                  TABLE 2                                                         ______________________________________                                         ##STR52##                                                                    ______________________________________                                        A:  1.                                                                                        ##STR53##                                                         2.                                                                                        ##STR54##                                                         3.                                                                                        ##STR55##                                                         4.                                                                                        ##STR56##                                                         5.                                                                                        ##STR57##                                                         6.                                                                                        ##STR58##                                                         7.                                                                                        ##STR59##                                                         8.                                                                                        ##STR60##                                                         9.                                                                                        ##STR61##                                                         10.                                                                                       ##STR62##                                                         11.                                                                                       ##STR63##                                                         12.                                                                                       ##STR64##                                                         13.                                                                                       ##STR65##                                                         14.                                                                                       ##STR66##                                                         15.                                                                                       ##STR67##                                                         16.                                                                                       ##STR68##                                                         17.                                                                                       ##STR69##                                                         18.                                                                                       ##STR70##                                                         19.                                                                                       ##STR71##                                                         20.                                                                                       ##STR72##                                                         21.                                                                                       ##STR73##                                                         22.                                                                                       ##STR74##                                                         23.                                                                                       ##STR75##                                                         24.                                                                                       ##STR76##                                                         25.                                                                                       ##STR77##                                                         26.                                                                                       ##STR78##                                                         27.                                                                                       ##STR79##                                                         28.                                                                                       ##STR80##                                                         29.                                                                                       ##STR81##                                                         30.                                                                                       ##STR82##                                                         31.                                                                                       ##STR83##                                                         32.                                                                                       ##STR84##                                                         33.                                                                                       ##STR85##                                                         34.                                                                                       ##STR86##                                                         35.                                                                                       ##STR87##                                                         36.                                                                                       ##STR88##                                                         37.                                                                                       ##STR89##                                                         38.                                                                                       ##STR90##                                                         39.                                                                                       ##STR91##                                                         40.                                                                                       ##STR92##                                                     ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                         ##STR93##                                                                    AB             X          R.sup.1 R.sup.2                                     ______________________________________                                         ##STR94##     (CH.sub.2).sub.4                                                                         H       H                                            ##STR95##     (CH.sub.2).sub.4                                                                         C.sub.2 H.sub.5                                                                       H                                            ##STR96##     (CH.sub.2).sub.4                                                                         C.sub.2 H.sub.5                                                                       COOCH.sub.2 Ph                               ##STR97##     (CH.sub.2).sub.3                                                                         H       H                                            ##STR98##     (CH.sub.2).sub.5                                                                         H       H                                           ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                         ##STR99##                                                                                AB                                                                ______________________________________                                                       ##STR100##                                                                    ##STR101##                                                                    ##STR102##                                                                    ##STR103##                                                                    ##STR104##                                                                    ##STR105##                                                                    ##STR106##                                                     ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                         ##STR107##                                                                           A:                                                                    ______________________________________                                                   ##STR108##                                                                    ##STR109##                                                                    ##STR110##                                                                    ##STR111##                                                                    ##STR112##                                                                    ##STR113##                                                                    ##STR114##                                                                    ##STR115##                                                                    ##STR116##                                                         10.                                                                                      ##STR117##                                                                    ##STR118##                                                                    ##STR119##                                                                    ##STR120##                                                                    ##STR121##                                                                    ##STR122##                                                                    ##STR123##                                                                    ##STR124##                                                                    ##STR125##                                                                    ##STR126##                                                         20.                                                                                      ##STR127##                                                                    ##STR128##                                                                    ##STR129##                                                                    ##STR130##                                                                    ##STR131##                                                                    ##STR132##                                                                    ##STR133##                                                                    ##STR134##                                                                    ##STR135##                                                                    ##STR136##                                                         30.                                                                                      ##STR137##                                                                    ##STR138##                                                                    ##STR139##                                                                    ##STR140##                                                                    ##STR141##                                                                    ##STR142##                                                                    ##STR143##                                                                    ##STR144##                                                                    ##STR145##                                                                    ##STR146##                                                         40.                                                                                      ##STR147##                                                                    ##STR148##                                                                    ##STR149##                                                                    ##STR150##                                                                    ##STR151##                                                                    ##STR152##                                                         ______________________________________                                         [wherein Ph is phenyl]-                                                  

R¹ is preferably hydrogen or lower alkyl; R² is desirably hydrogen; R³is favorably hydrogen; and R⁴ is preferably lower alkyl oramino-lower-alkyl or linked with A, more preferably lower alkyl. X ispreferably trimethylene, tetramethylene or pentamethylene; X is morepreferably tetramethylene.

A-B- is preferably a group represented by the formula: ##STR153##[wherein R^(4') is lower-(C₁₋₄)-alkyl], more preferably a grouprepresented by the formula (i) or (ii).

The compound (I) of this invention contains an asymmetric carbon atom inthe molecule, and its isomers with the R- and S-configurations and amixture thereof all fall within the scope of this invention.

The salt of the compound (I) includes pharmaceutically acceptable salts,such as inorganic acid salts being exemplified by hydrochloride,hydrobromide, sulfate, nitrate and phosphate; organic acid salts beingexemplified by acetate, tartarate, citrate, fumarate, maleate,toluenesulfonate and methanesulfonate; metal salts exemplified by sodiumsalt, potassium salt, calcium salt and aluminum salt; and salts withbases being exemplified by triethylamine salt, guanidine salt, ammoniumsalt, hydrazine salt, quinine salt and cinchonine salt.

The compound (I) of this invention can be produced, for example, bysubjecting a compound of the formula:

    A--H                                                       (II)

[wherein the symbol is as defined hereinbefore] and a compound of theformula: ##STR154## [wherein R^(1') is a lower alkyl or aralkyl groupcorresponding to R¹ ; R^(2') is an acyl group corresponding to R² ;other symbols are as defined hereinbefore] to a dehydration condensationreaction.

The said dehydration condensation reaction can be carried out, forexamples, by means of an ordinary amide bond formation reaction inpeptides. Thus, the reaction can be conducted by employing a peptideforming reagent solely, such as dicyclohexylcarbodiimide,N,N'-carbonyldiimidazole, diphenylphosphorylazide or diethylphosphorocyanidate or subjecting the compound (III) to condensation witha phenol compound such as 2,4,5-trichlorophenol, pentachlorophenol,pentafluorophenol, 2-nitrophenol or 4-nitrophenol, or an N-hydroxycompound, such as N-hydroxysuccinimide, 1-hydroxybenzotriazole orN-hydroxypiperidine, in the presence of a catalyst, such asdicyclohexylcarbodiimide to convert the compound (III) into an activeester derivative, followed by dehydration condensation with the compound(II). The said dehydration reaction, whether it comprises subjecting tothe reaction the compound (III) as such or after converting into anactive ester derivative, can be accelerated by adding preferably anorganic base, such as a quaternary ammonium salt or a tertiary amine(e.g., triethylamine, N-methylpiperidine). The reaction temperature isnormally -20° to +50° C., preferably in the neighborhood of roomtemperature, and the solvent to be ordinarily employed includes, forexample, dioxane, tetrahydrofuran, acetonitrile, pyridine,N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide,N-methylpyrrolidone, chloroform and methylene chloride, whereby thesemay be used singly or as a mixture thereof.

The compound (I) of this invention can also be produced, for example, byreacting a compound of the formula:

    A--B--NH.sub.2                                             (IV)

[wherein each of the symbols is as defined hereinbefore] with a compoundof the formula: ##STR155## [wherein R^(1'), R^(2') and X are as definedhereinbefore; W^(a) is halogen or a group represented by the formulaR^(a) --SO₂ --O-- (wherein R^(a) is lower-(C₁₋₄)-alkyl, trifluoromethyl,phenyl or p-tolyl); other symbols are as defined hereinbefore]. Thereaction can normally be allowed to proceed by maintaining the compoundsin the presence or absence of water of an organic solvent (e.g.,acetonitrile, dimethylformamide, dimethylsulfoxide, tetrahydrofuran,benzene, toluene), solely or as a mixture thereof, in the temperaturerange of about -20° to +150° C., whereby for the purpose of acceleratingthe reaction rate, a base, such as potassium carbonate, sodiumhydroxide, sodium hydrogencarbonate, pyridine or triethylamine, can alsobe allowed to coexist in the reaction system.

Alternatively, the compound (I) of this invention can be produced, forexample, by subjecting the compound of the formula (IV) and a compoundof the formula: ##STR156## [wherein each of the symbols is as definedhereinbefore] to a condensation reaction under reductive conditions.

The said reductive conditions include, for example, reaction conditions,such as catalytic reduction using a metal, such as platinum, palladium,rhodium or Raney nickel, or a mixture thereof with an arbitrary carrier(e.g., carbon, barium sulfate, calcium sulfate, barium carbonate,calcium carbonate) as a catalyst; reduction with a metal hydridecompound, such as lithium aluminum hydride, lithium borohydride, lithiumcyanoborohydride, sodium borohydride or sodium cyanoborohydride;reduction with metallic sodium, metallic magnesium, or the like and analcohol; reduction with a metal, such as iron or zinc, and an acid, suchas hydrochloric acid or acetic acid; electrolytic reduction; andreduction with a reducing enzyme. The above reaction is normally carriedout in the presence of water or an organic solvent (e.g., methanol,ethanol, ethyl ether, dioxane, methylene chloride, chloroform, benzene,toluene, acetic acid, dimethylformamide, dimethylacetamide), and thereaction temperature varies with means of reduction employed, butgenerally is preferably in the range of -20° C. to +100° C. Thisreaction can be conducted at atmospheric pressure to achieve the desiredobject satisfactorily but may also be carried out under pressure orunder reduced pressure according to the circumstances.

Also, the compound (I) of this invention can be produced, for example,by subjecting a compound of the formula: ##STR157## [wherein Z is aprotecting group removable by hydrolysis or catalytic reduction; andother symbols are as defined hereinbefore] to a hydrolysis or catalyticreduction reaction. As the protecting group removable by hydrolysis asrepresented by Z in the formula (VII), there are used all kinds of acyland trityl groups, and among others, benzyloxycarbonyl,tert-butoxycarbonyl, trifluoroacetyl, trityl, etc. are advantageous inthe case of a reaction under relatively mild reaction conditions. Theprotecting group removable by catalytic reduction as represented by Zincludes, for example, benzyl, diphenylmethyl and benzyloxycarbonyl. Thehydrolysis reaction in this procedure is carried out in water or anorganic solvent, such as methanol, ethanol, dioxane, pyridine, aceticacid, acetone or methylene chloride or a mixture thereof, and can alsobe conducted, for the purpose of accelerating the reaction rate, byadding an acid (e.g., hydrogen chloride, hydrogen bromide, hydrogeniodide, hydrogen fluoride, sulfuric acid, methanesulfonic acid,p-toluenesulfonic acid, trifluoroacetic acid) or a base (e.g., sodiumhydroxide, potassium hydroxide, potassium carbonate, sodiumhydrogen-carbonate, sodium acetate, triethylamine). The above reactionis normallly carried out in the temperature range of about -20° to +150°C. The catalytic reduction reaction in this procedure is conducted inwater or an organic solvent, such as methanol, ethanol, dioxane ortetrahydrofurane, or a mixture thereof in the presence of a suitablecatalyst, such as platinum or palladium-carbon. This reaction is carriedat atmospheric pressure or under pressure up to about 150 kg/cm² and atambient temperature or at a temperature up to +150° C., although itgenerally proceeds satisfactorily at ambient temperature and atatmospheric pressure.

Furthermore, the compound (I) of this invention can be produced bysolvolysis of the cyano group of a compound of the formula: ##STR158##[wherein each of the symbols is as defined hereinbefore].

The above solvolysis reaction is carried out in water or an organicsolvent, such as methanol, ethanol, dioxane, pyridine, acetic acid,acetone or methylene chloride, or a mixture thereof, and can also becarried out, for the purpose of accelerating the reaction rate, byadding an acid (e.g., hydrogen chloride, hydrogen bromide, hydrogeniodide, hydrogen fluoride, sulfuric acid, methanesulfonic acid,p-toluenesulfonic acid, trifluoroacetic acid, acidic resin) or a base(e.g., sodium hydroxide, potassium hydroxide, potassium carbonate,sodium hydrogencarbonate, sodium acetate, triethylamine). The reactionis normally carried out in the temperature range of about -20° to +150°C.

The compound of the formula (I) wherein R¹ is hydrogen or/and R³ ishydrogen can be produced by subjecting the compound of the formula (I)wherein R¹ is lower alkyl or/and R³ is lower alkyl to a hydrolysis orelimination reaction, and also by subjecting the compound of the formula(I) wherein R¹ is benzyl or/and R³ is benzyl to a catalytic reductionreaction. The hydrolysis or elimination reaction in this procedure iscarried out in water or an organic solvent, such as methanol, ethanol,ethyl acetate, chlorform, tetrahydrofuran, dioxane, pyridine, aceticacid, acetone or methylene chloride, or a mixture thereof, and can alsobe conducted by adding an acid (e.g., hydrogen chloride, hydrogenbromide, hydrogen fluoride, hydrogen iodide, sulfuric acid,methanesulfonic acid, p-toluenesulfonic acid, trifluoroacetic acid) or abase (e.g., sodium hydroxide, potassium hydroxide, potassium carbonate,sodium hydrogencarbonate, sodium carbonate, sodium acetate). The abovereaction is normally carried out in the temperature range of about -20°to +150° C. Also, the catalytic reduction reaction in this procedure isconducted in water or an organic solvent, such as methanol, ethanol,ethyl acetate, dioxane or tetrahydrofuran, or a mixture thereof, in thepresence of a suitable catalyst, such as palladium-carbon. This reactionis carried out at atmospheric pressure or under pressure up to about 150kg/cm² and at ambient temperature or at a temperature up to +150° C.

The compound of the formula (I) wherein R¹ is lower alkyl or aralkylor/and R³ is lower alkyl or aralkyl can be produced by subjecting thecompound of the formula (I) wherein R¹ is hydrogen or/and R³ is hydrogenand a compound of the formula:

    R.sup.1' --OH                                              (IX)

or a compound of the formula:

    R.sup.3' --OH                                              (X)

[wherein R^(1') and R^(3') are lower alkyl or aralkyl] to a condensationreaction.

The conditions of the said condensation reaction include, for example,reaction conditions, such as condensation using a condensing agent(e.g., dicyclohexylcarbodiimide, carbonyldiimidazole, diethylphosphorocyanidate, diphenyl phosphorylazide) or condensation employingan acid catalyst (e.g., hydrogen chloride, hydrogen bromide,p-toluenesulfonic acid). The reaction proceeds in the presence orabsence of a suitable solvent (e.g., dimethylformamide acetonitrile,tetrahydrofuran, methylene chloride) or a mixture thereof, in thetemperature range of about -20° to +150° C.

The compound of the formula (I) wherein R¹ is lower alkyl or aralkylor/and R³ is lower alkyl or aralkyl can also be produced by reacting thecompound of the formula (I) wherein R¹ is hydrogen or/and R³ is hydrogenwith a compound of the formula:

    R.sup.1" --W.sup.b                                         (XI)

or a compound of the formula:

    R.sup.3" --W.sup.b                                         (XII)

[wherein R^(1") and R^(3") are lower alkyl or aralkyl; W^(b) is halogenor a group represented by the formula R^(b) SO₂ --O-- (wherein R^(b) islower-(C₁₋₄)-alkyl, trifluoromethyl, phenyl or p-tolyl)]. The reactionproceeds in a suitable solvent (e.g., dimethylformamide, acetonitrile,dimethylsulfoxide, tetrahydrofuran) in the temperature range of about-20° to +150° C. in the presence of a base (e.g., potassium hydroxide,sodium hyroxide, sodium hydrogencarbonate, potassium hydrogencarbonate).

The compound (I) of this invention wherein the group R² is hydrogen canbe produced by subjecting the compound of the formula (I) wherein thegroup R² is benzyl or acyl to a catalytic reduction, elimination orsolvolysis reaction.

The catalytic reduction reaction in this procedure is carried out inwater or an organic solvent, such as methanol, ethyl acetate, ethanol,dioxane or tetrahydrofuran, or a mixture thereof in the presence of asuitable catalyst, such as palladium-carbon. This reaction is conductedat atmospheric pressure or under pressure up to about 150 kg/cm² and atambient temperature or at a temperature up to +150° C.

Also, the solvolysis or elimination reaction in this procedure iscarried out in water or an organic solvent, such as methanol, ethanol,ethyl acetate, chloroform, tetrahydrofuran, dioxane, pyridine, aceticacid, acetone and methylene chloride, or a mixture thereof, and can alsobe conducted by adding an acid (e.g., hydrogen chloride, hydrogenbromide, hydrogen fluoride, hydrogen iodide, sulfuric acid,methanesulfonic acid, p-toluenesulfonic acid, trifluoroacetic acid) or abase (e.g., sodium hydroxide, potassium hydroxide, potassium carbonate,sodium hydrogencarbonate, sodium carbonate, sodium acetate). The abovereaction is normally carried out in the temperature range of about -20°to +150° C.

The compound of the formula (I) wherein the group R² is lower alkyl,aralkyl or acyl can be obtained by reacting the compound of the formula(I) wherein R² is hydrogen with a compound of the formula:

    R.sup.2" --W.sup.c                                         (XIII)

[wherein R^(2") is lower alkyl, aralkyl or acyl; W^(c) is halogen or agroup represented by the formula R^(c) SO₂ --O-- (wherein R^(c) islower-(C₁₋₄)-alkyl, trifluoromethyl, phenyl or p-tolyl)]. The reactionproceeds by maintaining both of the compounds in a suitable solvent(e.g., dimethylformamide, acetonitrile, dimethylsulfoxide,tetrahydrofuran) in the temperature range of about -20° to +150° C. Inthis case, a base such as potassium carbonate, sodium hydroxide, sodiumhydrogencarbonate, pyridine or triethylamine can be allowed to coexistin the reaction system as a deacidifying agent for the purpose ofaccelerating the reaction rate.

Also, the compound of the formula (I) wherein the group R² is loweralkyl or aralkyl can be obtained by subjecting the compound of theformula (I) wherein the group R² is hydrogen and alower-(C₁₋₄)-alkylaldehyde or aralkylaldehyde [e.g.,phenyl-lower-(C₁₋₄)-alkylaldehydes] to condensation under reductiveconditions.

The said reductive conditions include, for example, reaction conditions,such as catalytic reduction using a metal, such as platinum, palladium,rhodium or Raney nickel, or a mixture thereof with an arbitrary carrier(e.g. carbon, barium sulfate, calcium sulfate, barium carbonate calciumcarbonate) as a catalyst; reduction with a metal hydride compound, suchas lithium aluminum hydride, lithium borohydride, lithiumcyanoborohydride, sodium borohydride or sodium cyanoborohydride;reduction with metallic sodium metallic magnesium, or the like and analcohol; reduction with a metal, such as iron or zinc, and an acid, suchas hydrochloric acid or acetic acid; electrolytic reduction andreduction with a reducing enzyme. The above reaction is normally carriedout in water or an organic solvent (e.g., methanol, ethanol, ethylether, dioxane, methylene chloride, chloroform, benzene, toluene, aceticacid, dimethylformamide, dimethylacetamide), and the reactiontemperature varies with the means of reduction employed, but generallyis preferably in the range of -20° C. to +100° C. This reaction can beconducted at atmospheric pressure to achieve the object satisfactorily,but may be carried out under pressure or under reduced pressureaccording to the circumstances.

The compound of the formula (I) wherein the group R² is acyl can also beproduced by reacting the compound of the formula (I) wherein the groupR² is hydrogen with a compound of the formula:

    (R.sup.2"').sub.2 O                                        (XIV)

[wherein R^(2"') is acyl corresponding to R² ].

The reaction is allowed to proceed by maintaining both of the compoundsin water or an organic solvent (e.g., ethyl acetate, ethyl ether,tetrahydrofuran, methylene chloride, chloroform, benzene) or a mixturethereof in the temperature range of about -20° to +150° C. In this case,a base such as potassium carbonate, sodium hydroxide, sodiumhydrogencarbonate, pyridine or triethylamine can also be allowed tocoexist in the reaction system as a deacidifying agent for the purposeof accelerating the reaction rate.

The salt of the compound (I) can be obtained by the production reactionfor the compound (I) itself, but can also be produced by adding an acid,alkali or base, if desired.

The objective compound (I) of this invention thus obtained can beisolated from the reaction mixture by employing conventional separationand purification means, such as extraction, concentration,neutralization, filtration, recrystallization, column chromatography andthin-layer chromatography.

With reference to the compound (I), at least two stereoisomers canexist. These individual stereoisomers and mixtures thereof all fallwithin the scope of this invention, and these isomers can be producedindividually, if desired. By carrying out the above reaction using asingle isomer each of the starting compounds (II), (III), (V), (V),(VII) and (VIII), for example, there can be obtained the single opticalisomer of the compound (I), and in cases in which the resulting productconsists of a mixture of at least two kinds of the isomers, it can beseparated into the invidual isomers by means of conventional separationprocedures, such as the procedure of forming salts with an opticallyactive acid (e.g., camphorsulfonic acid, tartaric acid, benzoyltartaricacid, etc.) or an optically active base (e.g., cinchonine, cinchonidine,quinine, quinidine, α-methylbenzylamine, dehydroabietylamine, etc.) andseparation means being exemplified by a variety of chromatography andfractionation recrystallization.

The compound of this invention, namely the compound represented by theformula (I) and a salt thereof, exhibit inhibitory activities onagiotensin converting enzyme, bradikinin decomposing enzyme (kininase),etc. in animals, in particular, mammals (e.g., human, dog, cat, rabbit,guinea pig, rat), and are useful, for example, as a drug for diagnosis,prevention or treatment for hypertension, hypertension-inducedcirculatory diseases, such as cardiopathy and cerebral apoplexy. Thecompound of this invention is low in toxicity, well absorbed even onoral administration and excellent in long-lasting effect and stability.Therefore, when the compound is used as the above-mentioned drug, it canbe safely administered orally or parenterally, per se or in admixturewith a suitable, pharmaceutically acceptable carrier, excipient ordiluent into a pharmaceutical formulation, such as powder, granule,tablet, capsule or injectable solution. The dosage level variesdepending upon the conditions of the disease to be treated andadministration route employed, but in the case of administration to anadult patient for the purpose of treatment of renal or essentialhypertension, for example, the compound is desirably administered orallyat a single dose of about 0.02 to 10 mg/kg, preferably about 0.02 to 2mg/kg, more preferably about 0.04 to 0.8 mg/kg, or intravenously at asingle dose of about 0.002 to 1 mg/kg, preferably about 0.02 to 1 mg/kg,more preferably about 0.02 to 0.2 mg/kg, about once to three times,preferably once to twice daily, according to the conditions beingtreated.

The starting compounds (III), (V), (VI), (VII) and (VIII) of thisinvention can be easily produced, for example, by the methods asillustrated in the following reaction schema: ##STR159##

In the above reaction schema, R⁵ is lower-(C₁₋₄)-alkyl or aralkyl [e.g.,phenyl-lower-(C₁₋₄)-alkyl], and other symbols are as definedhereinbefore.

Referring in more detail to the process for producing the compound (III)as illustrated in the above reaction schema, an α-amino acid tert-butylester (XV) being used as a starting compound is reacted with a compound(VI') under reductive conditions to produce a compound (XVI), followedby treatment of (XVI) with an acid (e.g., hydrogen chloride) to give thecompound (III).

In the processes for producing the compounds (V) and (VI), a compound(XVII) and a compound (XVIII) are subjected to condensation in thepresence of a base, such as sodium ethoxide, followed by heating inaqueous dimethylsulfoxide in the presence of lithium chloride, etc. toyield a compound (VI'). The compound (VI) can be easily obtained byhydrolysis, ester exchange, etc. of the compound (VI').

The compound (XIX) can be produced by subjecting the compound (VI') to aper se known reductive reaction. The reductive reaction includes, forexample, catalytic reduction; reduction with a metal hydride compoundsuch as lithium borohydride, sodium borohydride or sediumcyanoborohydride; reduction with metallic sodium, metallic magnesium,etc. and an alcohol; reduction with a metal such as iron or zinc and anacid; and electrolytic reduction. The compound (V) can be produced, forexample, by subjecting the compound (XIX) to a per se known halogenationor sulfonylation reaction.

A single isomer of the compound (I) can be produced by subjecting thecompound (VI') to an asymmetric reduction reaction and subjecting thesingle isomer of the compound (XIX) obtained to a per se knownhalogenation or sulfonylation reaction. The asymmetric reductionreaction includes, for example, a reduction with a microorganism or itsreducing enzyme, catalytic reduction with a catalyst ornamented by anasymmetric ligand and reduction with a metal hydride compound ornamentedby an asymmetric ligand.

The present invention also provides a method for asymmetric synthesis ofa compound of the formula ##STR160## wherein R representsR-configuration and other symbols are as defined hereinbefore, whichcomprises subjecting the compound (VI') to an asymmetric reductionreaction.

The microorganism or its reducing enzyme used for the present inventionincludes all microorganisms or their reducing enzymes having ability toasymmetrically reduce the compound (VI') to yield the compound (XIX'),but Baker's yeast is preferred, among others.

As the reaction mixture used for the present invention, an aqueoussolution (inclusive of a buffer) of pH 5 to 7 containing about 1-30 g/lof the compound (VI') is preferable. The aqueous solution may containabout 0-100 ml/l of an organic solvent such as alcohol (e.g. methanol,ethanol).

In case that the reducing enzyme is used, it is preferable that anamount of the enzyme equal to asymmetrically reduce the compound (VI')or an excess of the enzyme is added and then that the reaction iscarried out for about 0.5-24 hours.

In case that Baker's yeast, among the microorganisms, is used, it ispreferable that 1 to 500 gramms, preferably about 1 to 50 gramms, ofBaker's yeast per gram of the compound (VI') is added and then that thereaction is carried out at 15° to 40° C., preferably 25° to 35° C. for 1hour to 1 week. In case of use of a microorganism other than Baker'syeast, the reaction can be conducted in the manner similar to that ofBaker's yeast. As a carbon source in the asymmetric reduction reactionusing a microorganism, it is preferred that a sugar such as sucrose orglucose is added to the reaction mixture. If necessary, such substancesas Bactotrypton, yeast extract, Casamino Acids and ammonium sulfate.

After the reaction, the compound (XIX) can be extracted with ethylacetate, ether, alcohol, etc. without disrupting with cells or after thecells are disrupted by a surface active agent, lysozyme or mechanicaldistruct using glass beads. The compounds (XIX) after the asymmetricreduction reaction using a reducing enzyme can also be extracted in asimilar manner as mentioned above.

Among the compounds (VI') used for the asymmetic reduction reaction, thecompound of the formula (VI') wherein R^(1') is lower (C₁₋₄) alkyl,R^(2') is phenyl-lower (C₁₋₄) alkoxycarbonyl such as benzyloxycarbonyland X is tetramethylene.

The compound (VII) can be obtained by reacting the derivative (XX)having an amino group protected for example with the compound (V) toderive into a compound (XXI) and converting the compound (XXI). In theprocess for producing the compound (VIII), the compounds (IV) and(XXII), and hydrogen cyanide being used as starting compounds aretreated in accordance with the known Strecker reaction to give thecompound (VIII).

The compounds (II), (IV) and (XX) can be produced by the methods, ormethods similar thereto, as described in the literature [e.g.,Biochemical and Biophysical Research Communications, 117, 108 (1983):Federation of European Biochemical Societies, 165, 201 (1984): Journalof Medicinal Chemistry, 26, 1267 (1983): Tetrahedron Letters, 24, 5339(1983): Tetrahedron Letters, 25, 4479 (1984): Tetrahedron Letters, 25,4483 (1984): Japanese Unexamined Patent Publication No. 192395/1982;Japanese Unexamined Patent Publication No. 55451/1983; JapaneseUnexamined Patent Publication No. 231052/1984: Japanese UnexaminedPatent Publication No. 153769/1980: Japanese Unexamined PatentPublication No. 188857/1983: Japanese Unexamined Patent Publication No.203050/1982: Japanese Unexamined Patent Publication No. 88165/1982:Japanese Unexamined Patnet Publication No. 147257/1980: JapaneseUnexamined Patent Publication No. 206387/1984: Japanese UnexaminedPatent Publication No. 59175/1980: Japanese Unexamined PatentPublication No. 130268/1984: Japanese Unexamined Patent Publication No.172367/1983: Japanese Unexamined Patent Publication No. 29686/1984:Japanese Unexamined Patent Publication No. 118766/1984: JapaneseUnexamined Patent Publication No. 134765/1984: Japanese UnexaminedPatent Publication No. 177967/1983: Japanese Unexamined PatentPublication No. 177968/1983: Japanese Unexamined Patent Publication No.45155/1980: Japanese Unexamined Patent Publication No. 27199/1980:Japanese Unexamined Patent Publication No. 101463/1984: European PatentApplication laid open No. 68173: Britisih patent application laid openNo. 2095682: European patent application laid open No. 51391: Europeanpatent application laid open No. 57998: South African Republic Pat. No.836736].

Also, the compounds (V), (VI), (XVII) and (XXII) can be produced, forexample, by the methods, or methods similar thereto, as described inU.S. patent application Ser. Nos. 637,620 filed on Aug. 3, 1984 and691,005 filed on Jan. 14, 1985.

The following Examples are illustrating this invention but thisinvention is not limited to them.

EXAMPLE 1

A solution of 0.6 g of sodium cyanoborohydride in 50 ml of ethanol isadded dropwise to a stirred mixture of 2 g ofN-(L-alanyl)-N-(2-indanyl)glycine tert-butyl ester oxalate, 078 g ofsodium acetate, 0.58 g of acetic acid, 10 g of molecular sieves 3A, 3.6g of ethyl 6-(1-benzyloxycarbonyl-4-piperidyl)-2-oxohexanoate and 50 mlof ethanol at room temperature over a period of 3 hours. The reactionsolution is allowed to stand overnight and filtered, and the filtrate isconcentrated under reduced pressure. The residue is diluted with 50 mlof water and extracted with 200 ml of ethyl acetate. The extract isdried and concentrated under reduced pressure. The resulting oilymaterial is separated and purified by silica gel column chromatography(hexane:ethyl acetate=1:1 to 2:3), whereby the first fraction yields0.35 g ofN-[N-[(R)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-N-(indan-2-yl)glycinetert-butyl ester as a colorless oil.

IR ν_(max) ^(neat) cm⁻¹ : 3320(NH): 1730, 1690, 1650 (C═O).

Mass spectrum (m/e): 677 (M⁺).

NMR spectrum δ(in CDCl₃): 7.3 (5H, phenyl proton of benzyloxycarbonylgroup), 7.2 (4H, phenyl proton of indanyl group), 5.1 (2H, methyleneproton of benzyloxycarbonyl group), 1.4 (9H, methyl proton of tert-butylgroup).

The subsequent second fraction provides 0.4 g ofN-[N-[(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-N-(indan-2-yl)glycinetert-butyl ester as a colorless oil.

IR ν_(max) ^(neat) cm⁻¹ : 3320 (NH): 1760, 1690, 1640 (C═O).

Mass spectrum (m/e): 677 (M⁺).

NMR spectrum δ(in CDCl₃): 7.3 (5H, phenyl proton of benzyloxycarbonylgroup), 7.1 (4H, phenyl proton of indanyl group), 5.1 (methylene protonof benzyloxycarbonyl group), 1.4 (methyl proton of tert-butyl group).

EXAMPLE 2

In 2 ml of acetic acid is dissolved 0.35 g ofN-[N-[(R)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-N-(indan-2-yl)glycinetert-butyl ester, and 2 ml of 30% hydrogen bromide-acetic acid solutionis added to the solution, followed by standing at room temperature for 1hour. 50 ml of ethyl ether is added to the reaction mixture, followed byshaking, and the supernatant layer is removed by decantation. Thecolorless precipitate is rinsed with ethyl ether and dried under reducedpressure to give 0.3 g ofN-[N-[(R)-1-ethoxycarbonyl-5-(4-piperidyl)pentyl]-L-alanyl]-N-(indan-2-yl)glycine.dihydrobromideas a colorless powder.

Elemental analysis for C₂₇ H₄₁ N₃ O₅ 2HBr 4H₂ O: Calcd.: C, 44.94; H,7.13; N, 5.82. Found: C, 45.33; H, 6.97; N, 5.72.

[α]_(D) -7.9° (in methanol).

SIMS spectrum (m/e): 488 (MH⁺).

EXAMPLE 3

In 2 ml of acetic acid is dissolved 0.4 g ofN-[N-[(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-N-(indan-2-yl)glycinetert-butyl ester, and 2 ml of 30% hydrogen bromide-acetic acid solutionis added to the solution, followed by standing at room temperature for 1hour. 50 ml of ethyl ether is added to the reaction mixture, followed byshaking, and the supernatant layer is removed by decantation. Thecolorless precipitate is rinsed with ethyl ether and dried under reducedpressure to give 0.3 g ofN-[N-[(S)-1-ethoxycarbonyl-5-(4-piperidyl)pentyl]-L-alanyl]-N-(indan-2-yl)glycinedihydrobromide as a colorless powder.

Elemental analysis for C₂₇ H₄₁ N₃ O₅.2HBr.3H₂ O: Calcd.: C, 46.09; H,7.01; N, 5.97. Found: C, 46.19; H, 6.95; N, 5.91.

[α]_(D) +2.6° (in methanol).

SIMS spectrum (m/e): 488 (MH⁺).

EXAMPLE 4

In 210 ml of tetrahydrofuran is dissolved 26.1 g ofN-benzyloxycarbonyl-L-alanine, and a solution of 16.4 ml oftriethylamine in 20 ml of tetrahydrofuran is added dropwise to thesolution at the temperature below -10° C. with stirring. Then, asolution of 11.2 ml of ethyl chlorocarbonate in 20 ml of tetrahydrofuranis added dropwise to the solution. After stirring for 20 minutes, asolution of 15.4 g of L-proline tert-butyl ester in 102 ml of chloroformis added dropwise to the mixture at the temperature below -10° C. over aperiod of 48 minutes. After the addition is completed, stirring iscontinued for 1 hour under cooling and for 1.5 hours at roomtemperature. The reaction solution is poured into 600 ml of ice-water,and the chloroform layer is separated and concentrated under reducedpressure. The residue is dissolved in 304 ml of ethyl acetate, and thesolution is washed with 1N aqueous sodium hydroxide, saturated aqueoussodium chloride, 20% aqueous phosphoric acid and saturated aqueoussodium chloride, successively. The ethyl acetate layer is dried overanhydrous magnesium sulfate, and concentrated under reduced pressure togive 33.8 g of N-(N-benzyloxycarbonyl-L-alanyl)-L-proline tert-butylester as an oil. This product is dissolved in 304 ml of methanolcontaining 8.12 g of oxalic acid, and 10% palladium-carbon (50% wet, 3.6g) are added to the solution to conduct catalytic reduction at ambienttemperature and under atmospheric pressure. The catalyst is filteredoff, and the filtrate is concentrated under reduced pressure. 400 ml ofethyl ether is added to the residue, and the crystals which separate outare collected by filtration to give 20.2 g of N-(L-alanyl)-L-prolinetert-butyl ester.oxalate as a colorless powder.

[α]_(D) ²⁴ -84.1° (c=1, in methanol).

Elemental analysis, for C₁₂ H₂₂ N₂ O₃.C₂ H₂ O₄.1/2H₂ O: Calcd.: C,49.25; H, 7.38; N, 8.21. Found: C, 48.95; H, 6.94; N, 8.05.

EXAMPLE 5

A solution of 0.57 g of sodium cyanoborohydride in 40 ml of ethanol isadded dropwise to a stirred mixture of 2 g of N-(L-alanyl)-L-prolinetert-butyl ester. oxalate, 1 of sodium acetate, 0.72 g of acetic acid,10 g of molecular sieves 3A, 3.4 g of ethyl6-(1-benzyloxycarbonyl-4-piperidyl)-2-oxohexanoate and 50 ml of ethanolat room temperature over a period of 2 hours. The reaction mixture isallowed to stand overnight and filtered, and the filtrate isconcentrated under reduced pressure. The resulting oily material ispurified by silica gel column chromatography (hexane:ethyl acetate=1:1to hexane:acetone=1:1) to give 0.66 g ofN-[N-[5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-L-prolinetert-butyl ester as a colorless oil.

IR ν_(max) ^(neat) cm⁻¹ : 3325 (NH): 1730, 1690, 1650 (C═O).

Mass spectrum (m/e): 601 (M⁺).

NMR spectrum δ(in CDCl₃): 7.3 (5H, phenyl proton of benzyloxycarbonylgroup), 5.1 (2H, methylene proton of benzyloxycarbonyl group), 1.4 (9H,methyl proton of tert-butyl group).

EXAMPLE 6

In 1.5 ml of acetic acid is dissolved 0.66 g ofN-[N-[5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-L-prolinetert-butyl ester, and 2 ml of 30% hydrogen bromide-acetic acid solutionis added to the solution, followed by standing at room temperature for 1hour. 50 ml of ethyl ether is added to the reaction solution, followedby shaking, and the precipitate is rinsed twice with 50 ml of ethylether. The resulting yellow, viscous material is dissolved in 5 ml ofwater, and the solution is extracted with 10 ml of ethyl acetate. Theaqueous layer is lyophilized to give 0.4 g ofN-[N-1-ethoxycarbonyl-5-(4-piperidyl)pentyl]-L-alanyl-L-proline.dihydrobromide.

Elemental analysis, for C₂₁ H₃₇ N₃ O₅.2HBr.4H₂ O: Calcd.: C, 39.08; H,7.34; N, 6.51. Found: C, 39.43; H, 7.10; N, 6.50.

EXAMPLE 7

In 20 ml of methanol is dissolved 0.4 g ofN-[N-[(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-N-(indan-2-yl)glycinetert-butyl ester, and a catalytic reduction is carried out at ambienttemperature and under atmospheric pressure using 10% palladium-carbon(50% wet, 0.4 g) as a catalyst. After stirring at room temperature for 4hours, the catalyst is removed by filtration, and the filtrate isconcentrated under reduced pressure to give 0.3 ofN-[N-[(S)-5-(4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-N-(indan-2-yl)glycinetert-butyl ester as a colorless oil.

EXAMPLE 8

In 2 mol of acetic acid is dissolved 0.3 g ofN-[N-[(S)-5-(4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-N-(indan-2yl)glycinetert-butyl ester, and 1 ml of hydrogen bromide-acetic acid solution isadded to the solution, followed by standing at room temperature for 30minutes. 50 ml of ethyl ether is added to the reaction solution,followed by shaking, and the supernatant layer is removed bydecantation. The precipitate is collected and dried under reducedpressure to give 0.3 g ofN-[N-[(S)-1-ethoxycarbonyl-5-(4-piperidyl)pentyl]-L-alanyl]-N-(indan-2-yl)glycine.dihydrobromideas a colorless powder.

EXAMPLE 9

In 6 ml of 1N aqueous sodium hydroxide is dissolved 0.25 g ofN-[N-[(S)-1-ethoxycarbonyl-5-(4-piperidyl)pentyl]-L-alanyl]-N-(indan-2-yl)glycine.dihydrobromide,and the solution is allowed to stand at room temperature for 30 minutes.The reaction is made weakly acidic with acetic acid and purified bycolumn chromatography on Amberlite XAD-2 (0.1M aqueous ammonia-5%acetonitrile). The effluent is concentrated under reduced pressure andlyophilized to give 0.11 g ofN-[N-[(S)-1-carboxy-5-(4-piperidyl)pentyl]-L-alanyl]-N-(indan-2-yl)glycineas a colorless powder.

[α]_(D) ²⁴ +6.1° (c=0.4 in water).

Elemental analysis, for C₂₅ H₃₇ N₃ O₅.2H₂ O: Calcd.: C, 60.59; H, 8.34;N, 8.48. Found: C, 60.37; H, 7.99; N, 8.70.

SIMS spectrum (m/e): 460 MH⁺).

EXAMPLE 10

In 20 ml of methanol is dissolved 0.55 g ofN-[N-[(S)-5-(1-benxzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-N-(indan-2-yl)glycinetert-butyl ester, and 5 ml of 1N of aqueous sodium hydroxide is addeddropwise to the solution over a period of 5 minutes. After stirring atroom temperature for 1 hour, another 2 ml of 1N aqueous sodium hydroxideis added dropwise to the mixture over a period of 5 hours. After 2 ml ofwater is added dropwise over a period of 2 hours, 10 ml of water isadded to the reaction solution, and the mixture is extracted with 10 mlof n-hexane. The aqueous layer is made weakly acidic with 1Nhydrochloric acid, and extracted with 50 ml of ethyl acetate. Theextract is washed with water, dried over anhydrous magnesium sulfate andconcentrated under reduced pressure to give 0.5 g ofN-[N-[(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-carboxypentyl]-L-alanyl]-N-(indan-2-yl)glycinetert-butyl ester as a colorless oil.

SIMS spectrum (m/e): 650 (MH⁺).

EXAMPLE 11

In 20 ml of methanol is dissolved 0.5 g ofN-[N-[(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-carboxypentyl]-L-alanyl]-N-(indan-2-yl)glycinetert-butyl ester, and a catalytic reduction is carried out at ambienttemperature and under atmospheric pressure using 10% palladium-carbon(50% wet., 0.5 g) as a catalyst. After stirring at room temperature for4 hours, the catalyst is filtered off, and the filtrate is concentratedunder reduced pressure to give 0.28 g ofN-[N-[(S)-5-(4-piperidyl)-1-carboxypentyl]-L-alanyl]-N-(indan-2-yl)glycinetert-butyl ester as a colorless powder.

Mass spectrum (m/e): 515 (M⁺).

EXAMPLE 12

In a mixture of 2 ml of acetic acid and 2 ml of ethyl acetate isdissolved 0.28 g ofN-[N-[(S)-5-(4-piperidyl)-1-carboxypentyl]-L-alanyl]-N-(indan-2-yl)glycinetert-butyl ester, and 5 ml of 5N hydrogen choride-ethyl acetate solutionis added to the solution, followed by standing at room temperature for 1hour. 100 ml of ethyl ether is added to the reaction solution, and theprecipitate which separates out is colleted by filtration to give 0.22 gofN-[N-[(S)-1-carboxy-5-(4-piperidyl)pentyl]-L-alanyl]-N-(indan-2yl)glycine.dihydrochlorideas a colorless powder.

EXAMPLE 13

A mixture of 5 g of L-alanine tert-butyl ester.oxalate, 11 g of ethyl6-(1-benzyloxycarbonyl-4-piperidyl)-2-oxohexanoate, 1.6 g of sodiumacetate, 1.2 g of acetic acid and 100 ml of ethanol is stirred at roomtemperature for 1 hour, and a solution of 1.9 g of sodiumcyanoborohydride in 100 ml of ethanol is added dropwise to the mixtureover a period of 4 hours. After stirring at room temperature overnight,500 ml of water is added to the reaction mixture, and the mixture isextracted with 300 ml of ethyl acetate. The extract is washed withwater, dried over anhydrous magnesium sulfate and concentrated underreduced pressure. The residue is separated and purified by silica gelcolumn chromatography (hexane:acetone=4:1), whereby the first fractionyields 1.7 g ofN-[(R)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alaninetert-butyl ester as a colorless oil.

IR ν_(max) ^(neat) cm⁻¹ : 3350 (NH); 1730, 1700 (C═O).

Mass spectrum (m/e): 504 (M⁺).

NMR spectrum δ (in CDCl₃): 7.3 (5H, phenyl proton of benzyloxycarbonylgroup), 5.1 (2H, s, methylene proton of benzyloxycarbonyl group), 1.45(9H, s, methyl proton of tert-butyl group).

The second fraction provides 1.5 g ofN-[(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alaninetert-butyl ester as a colorless oil.

IR νhd max^(neat) cm⁻¹ : 3350 (NH); 1730, 1700 (C═O).

NMR δ (in CDCl₃ 9: 7.2 (5H, phenyl proton of benzyloxycarbonyl group),5.1 (2H, s, methylene proton of benzyloxycarbonyl group), 1.45 (9H, s,methyl proton of tert-butyl group).

Mass spectrum (m/e): 504 (M⁺).

EXAMPLE 14

In 20 ml of 5N hydrogen chloride-ethyl acetate solution is dissolved 1.7g ofN-[(R)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alaninetert-butyl ester, and the solution is allowed to stand at roomtemperature for 4 hours. 100 ml of ethyl ether is added to the reactionsolution, and the colorless powder, which separates out, is collected byfiltration to give 1.2 g ofN-[(R)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanine.hydrochloride.

Elemental analysis, for C₂₄ H₃₆ N₂ O₆.HCl.H₂ O: Calcd.: C, 57.31; H,7.81; N, 5.57. Found: C, 56.91; H, 7.85; N, 5.92.

[α]_(D) ²⁴ -9.9° (c=0.5, in methanol).

Mass spectrum (m/e): 448 (M⁺).

EXAMPLE 15

In 30 ml of 5N hydrogen chloride-ethyl acetate solution is dissolved 1.5g ofN-[(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alaninetert-butyl ester, and the solution is allowed to stand at roomtemperature for 5 hours. The reaction solution is concentrated todryness under reduced pressure, and the residue is rinsed with ethylether and dried under reduced pressure to give 1.15 g ofN-[(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanine.hydrochlorideas a colorless gum.

Elemental analysis, for C₂₄ H₃₆ N₂ O₆.HCl.H₂ O: Calcd.: C, 57.31; H,7.81; N, 5.57. Found: C, 57.19; H, 8.06; N, 5.61.

[α]_(D) ²⁴ +12.7° (c=0.5, in methanol).

Mass spectrum (m/e): 448 (M⁺).

EXAMPLE 16

In 2 ml of N,N-dimethylformamide are dissolved 25 mg ofN-(2-indanyl)glycine tert-butyl ester and 50 mg ofN-[(R)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanine.hydrochloride,and 0.1 ml of diethyl phosphorocyanidate is added to the solution underice-cooling with stirring. After stirring for 30 minutes, 0.1 ml oftriethylamine is added to the mixture, followed by stirring underice-cooling for 30 minutes and then stirring at room temperature for 30minutes. 50 ml of water is added to the reaction solution, and themixture is extracted with 30 ml of ethyl acetate. The extract is driedover anhydrous magnesium sulfate and concentrated under reducedpressure. The residue is purified by silica gel column chromatography(hexane:ethyl acetate=1:1) to give 30 mg ofN-[N-(R)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-N-(indane-2-yl)glycinetert-butyl ester as a colorless oil.

EXAMPLE 17

In 2 ml of N,N-dimethylformamide are dissolved 25 mg ofN-(2-indanyl)glycine tert-butyl ester and 50 mg ofN-[(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanine.hydrochloride,and 0.1 ml of diethyl phosphorocyanidate is added to the solution underice-cooling with stirring. After stirring for 30 minutes, 0.1 ml oftriethylamine is added to the mixture, followed by stirring underice-cooling for 30 minutes and then stirring at room temperature for 30minutes. 50 ml of water is added to the reaction solution, and themixture is extracted with 30 ml of ethyl acetate. The extract is driedover anhydrous magnesium sulfate and concentrated under reducedpressure. The residue is purified by silica gel column chromatography(hexane:ethyl acetate=1:1) to give 35 mg ofN-[N-(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-N-(indan-2yl)glycinetert-butyl ester as a colorless oil.

EXAMPLE 18

In 20 ml of N,N-dimethylformamide are dissolved 0.4 g of tert-butyl(S)-1,2,3,4-tetrahydroisoquinoline-3-carboxylate hydrochloride and 0.4 gofN-[(S)-5-(1-benxyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanine.hydrochloride,and 0.4 ml of diethyl phosphorocyanidate is added dropwise to thesolution under ice-cooling with stirring. After stirring for 30 minutes,0.4 ml of triethylamine is added dropwise to the mixture, followed bystirring under ice-cooling for 1 hour and then at room temperature for30 minutes. 200 ml of water is added to the reaction mixture, and themixture is extracted with 200 ml of ethyl acetate. The extract is washedwith 5% aqueous phosphoric acid and water, successively, dried overanhydrous magnesium sulfate and concentrated under reduced pressure. Theresidue is purified by silica gel column chromatography(hexane:acetone=2:1) to give 0.37 g of tert-butyl(S)-2-[N-(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxylateas a colorless oil.

IR ν_(max) ^(neat) cm⁻¹ : 1730, 1690, 1640 (C═O).

NMR δ (in CDCl₃): 7.0-7.3 (9H, phenyl proton), 5.1 (2H, s, methyleneproton of benzyloxycarbonyl group, 1.2 (9H, s, methyl proton oftert-butyl group).

Mass spectrum (m/e): 663 (M⁺).

EXAMPLE 19

In 1 ml of acetic acid is dissolved 0.37 g of tert-butyl(S)-2-[N-(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxylate,and 2 ml of 30% hydrogen bromide-acetic acid solution is added to thesolution, followed by standing at room temperature for 1 hour. 50 ml ofethyl ether is added to the reaction solution, followed by shaking.After standing, the supernantant layer is removed by decantation. Theprecipitate is collected and dried under reduced pressure to give 0.36 gof(S)-2-[N[(S)-1-ethoxycarbonyl-5-(4-piperidyl)pentyl]-L-alanyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxylicacid.dihydrobromide as a colorless powder.

[α]_(D) ²⁵ +5.8° (c=0.4, in MeOH).

SIMS spectrum (m/e): 474 (MH⁺); 512 (M+K)⁺ (addition of KI).

EXAMPLE 20

In 8 ml of 1N aqueous sodium hydroxide is dissolved 0.3 g of(S)-2-[N-(S)-1-ethoxycarbonyl-5-(4-piperidyl)pentyl]-L-alanyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxylicacid.dihydrobromide, and the solution is allowed to stand at roomtemperature for 1 hour. The reaction solution is made acidic with 1 mlof acetic acid, and then purified by Amberlite XAD-2 columnchromatography (0.1M aqueous ammonia-5% acetonitrile). The effluent isconcentrated under reduced pressure, and lyophilized to give 0.16 g of(S)-2-[N-[(S)-1-carboxy-5-(4-piperidyl)pentyl]-L-alanyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxylicacid as a colorless powder.

SIMS spectrum (m/e): 446 (MH⁺); 484 (M+K)⁺, 522 (M+2K)⁺ (addition ofKI).

EXAMPLE 21

In 30 ml of N,N-dimethylformamide are dissolved 2.4 g of L-prolinetert-butyl ester and 5.87 g of N.sup.α -benzyloxycarbonyl-N.sup.ε-tert-butoxycarbonyl-L-lysine, and 3 g of diethyl phosphorocyanidate isadded dropwise to the solution under ice-cooling. After stirring for 30minutes, a solution of 1.42 g of triethylamine in 5 ml ofN,N-dimethylformamide is added to the mixture, followed by stirringunder ice-cooling for 1 hour and then at room temperature for 2 hours.500 ml of water is added to the reaction mixture, and the mixture isextracted with 300 ml of ethyl acetate. The extract is washed withaqueous dilute phosphoric acid, 0.1N aqueous sodium hydroxide and water,successively, dried over anhydrous magnesium sulfate and concentratedunder reduced pressure. The resulting oily material is purified bysilica gel column chromatography (hexane:ethyl acetate=2:1 to 1:1) togive 5.5 of N-(N.sup.α -benzyloxycarbonyl-N.sup.ε-tert-butoxycarbonyl-L-lysyl)-L-proline tert-butyl ester as a colorlessoil.

Mass spectrum (m/e): 533 (M⁺).

In 50 ml of methanol is dissolved 2.5 g of this product, and a catalyticreduction is carried out at ambient temperature and under atmosphericpressure using 10% palladium-carbon (50% wet, 1 g) as a catalyst, Afterthe absorption of hydrogen is observed to stop, the catalyst is removedby filtration, and the filtrate is concentrated under reduced pressure.A solution of 0.5 g of oxalic acid in 50 ml of ethyl ether is added tothe resulting oily material to give 1.5 g of N-(N.sup.ε-tert-butoxycarbonyl-L-lysyl)-L-proline tert-butyl ester.oxalate ascolorless scales.

m.p. 154°-156° C.

Elemental analysis, for C₂₀ H₃₇ N₃ O₅.(COOH)₂.H₂ O: Calcd.: C, 52.05; H,8.14; N, 8.28. Found: C, 51.93; H, 7.67; N, 8.10.

EXAMPLE 22

A mixture of 0.4 g of N-(N.sup.ε -tert-butoxycarbonyl-L-lysyl)-L-prolinetert-butyl ester.oxalate, 1.5 g of ethyl6-(1-benzyloxy-4-piperidyl-2-oxohexanoate, 0.07 g of sodium acetate,0.05 g of acetic acid and 30 ml of ethanol is stirred at roomtemperature for 30 minutes, and a solution of 0.05 g of sodiumcyanoborohydride in 10 ml of ethanol is added dropwise to the mixture atroom temperature over a period of 4 hours. Furthermore, a solution of0.2 g of sodium cyanoborohydride in 40 ml of ethanol is added dropwiseto the mixture over a period of 3 hours, followed by stirring overnight.500 ml of water is added to the reaction solution, and the mixture isextracted with ethyl acetate. The extract is washed with water, driedover anhydrous magnesium sulfate and concentrated under reducedpressure. The residue is purified by silica gel column chromatography(hexane:acetone=3:1) to give 0.43 g of N-[N.sup.α-[5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-N.sup..epsilon.-tert-butoxycarbonyl-L-Zlysyl]-L-proline tert-butyl ester as a colorlessoil.

IR ν_(max) ^(neat) cm⁻¹ : 3350 (NH); 1730, 1700, 1630 (C═O).

NMR spectrum δ (in CDCl₃): 7.25 (5H, pehnylproton of benzyloxycarbonylgroup), 5.1 (2H, s, methylene proton of benzyloxycarbonyl group), 1.4(18H, s, methyl proton of tert-butyl group).

Mass spectrum (m/e): 758 (M⁺).

EXAMPLE 23

In 1 ml of acetic acid is dissolved 0.43 g of N-[N.sup.α-[5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-N-.sup..epsilon.-tert-butoxycarbonyl-L-lysyl]-L-proline tert-butyl ester, and 2 ml of30% hydrogen bromide-acetic acid solution is added to the solution,followed by standing at room temperature for 1 hour. 50 ml of ethylether is added to the reaction solution, followed by shaking, and thesupernatant layer is removed by decantation. The precipitate iscollected and dried under reduced pressure to give 0.3 g of N-[N.sup.α-[1-ethoxycarbonyl-5-(4-piperidyl)pentyl]-L-lysyl]-L-proline.trihydrobromideas a colorless powder.

Elemental analysis, for C₂₄ H₄₄ N₄ O₅.3HBr.4H₂ O: Calcd.: C, 36.79; H,7.08; N, 7.15. Found: C, 37.27; H, 7.07; N, 6.72.

SIMS spectrum (m/e): 469 (MH⁺), 5.07 (M+K)⁺, KI added.

EXAMPLE 24

In an aqueous solution (150 ml) of 6.1 g of sodium carbonate isdissolved 11.7 g of 2-amino-4-(2-nitrophenyl)butyric acid, and 15 g ofN-ethoxycarbonylphthalimide is added to the solution under stirring.After stirring at room temperature overnight, the insoluble material isremoved by filtration, and the filtrate is made weakly acidic withconcentrated hydrochloric acid. The viscous material, which separatesout, is admixed with 50 ml of ethanol, followed by stirring, wherebythere separate out crystals. The crystals are collected by filtrationand dried to give 13 g of 4-(2-nitrophenyl)-2-phtalimidobutyric acid ascolorless crystals. m.p. 177°-179° C.

Elemental analysis, for C₁₈ H₁₄ N₂ O₆ : Calcd.: C, 61.02;l H, 3.98; N,7.91. Found: C, 61.04; H, 3.98; N, 7.82.

IR spectrum ν_(max) ^(nujol) cm⁻¹ : 1780, 1730, 1720 (C═O).

EXAMPLE 25

In 300 ml of methanol, 13 g of 4-(2-nitrophenyl)-2-phthalimidobutyricacid is catalytically reduced at ambient temperature and underatmospheric pressure with use of 3 g of 5% palladium-carbon as acatalyst. After the calculated amount of hydrogen is absorbed, theinsoluble material is separated by filtration, and washed four timeswith 300 ml of acetone. The acetone washings and the methanol portionare combined and concentrated under reduced pressure. The residue isadmixed with 50 ml of ethanol, and the crystals which separate out arecollected by filtration to give 10.1 g of4-(2-aminophenyl)-2-phthalimidobutyric acid as yellow prisms. m.p.198°-203° C. (decomp.).

Elemental analysis, for C₁₈ H₁₆ N₂ O₄ : Calcd.: C, 66.66; H, 4.97; N,8.64. Found: C, 66.16; H, 4.97; N, 8.71.

IR specrrum ν_(max) ^(nujol) cm⁻¹ : 3380, 3300 (NH); 1770, 1710 (C═O).

EXAMPLE 26

In 80 ml of N,N-dimethylformamide is dissolved 10 g of4-(2-aminophenyl)-2-phthalimidobutyric acid, and 6.7 g of diethylphosphorocyanidate is added dropwise to the solution under ice-coolingwith stirring. After the addition is complete, stirring is continued for15 minutes, and 3.1 of triethylamine is added dropwise to the mixtureunder ice cooling, followed by stirring under ice-cooling for 45 minutesand then at room temperature for 30 minutes. The reaction solution isdiluted with 200 ml of water, followed by stirring for 1 hour, and thecrystals, which separate out, are collected by filtration, dried andadded to 100 ml of ethanol, followed by heating. After the solution isconcentrated to about half of the original volume, the colorless prismswhich separate out are collected by filtration to give 8.3 g of3-phthalimido-1,3,4,5-tetrahydro-1-benzazepin-2-one. m.p. 261°-263° C.

Elemental analysis, for C₁₈ H₁₄ N₂ O₃ : Calcd.: C, 70.58; H, 4.61; N,9.15. Found: C, 70.28; H, 4.66; N, 9.12.

IR spectrum ν_(max) ^(nujol) cm⁻¹ : 1770, 1710, 1680 (C═).

EXAMPLE 27

In 50 ml of N,N-dimethylformamide is dissolved 8.3 g of3-phthalimido-1,3,4,5-tetrahydro-1-benzazepin-2-one, and 6.1 g oftert-butyl chloroacetate, 8 g of potassium carbonate and 2 g ofpotassium iodide are added to the solution, followed by stirring at roomtemperature overnight. The reaction solution is diluted with 300 ml ofwater, extracted with 500 ml of methylene chloride. The extract iswashed with water, 1N hydrochloric acid and water, successively, driedover anhydrous magnesium sulfate and concentrated under reducedpressure. 50 ml of ethanol is added to the residue, whereby thereseparates out tert-butyl2-oxo-3-phthalimido-2,3,4,5-tetrahydro-1H-1-benzazepine-1-acetate ascrystals. Collection by filtration yields 10.2 g of colorless prisms,m.p. 203°-205° C.

Elemental analysis, for C₂₄ H₂₄ N₂ O₅ : Calcd.: C, 68.56; H, 5.75; N,6.66. Found: C, 68.27; H, 5.71; N, 6.38.

IR spectrum ν_(max) ^(nujol) cm⁻¹ : 1770, 1740, 1720, 1680 (C═O).

EXAMPLE 28

To 100 mol of ethanol is added 10 g of tert-butyl2-oxo-3-phthalimido-2,3,4,5-tetrahydro-1H-1-benzazepine-1-acetate, and 5g of hydrazine hydrate is added to the mixture, followed by refluxingfor 2 hours. The reaction mixture is concentrated under reducedpressure, and 300 ml of water is added to the residue, followed byextraction with 200 ml of ethyl acetate. The extract is washed with 1Naqueous sodium hydroxide and water, successively, dried over anhydrousmagnesium sulfate and concentrated under reduced pressure. The crystals,which separate out, are treated with a mixture of ether and petroleumether and collected by filtration to give 6 g of tert-butyl3-amino-2-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-1-acetate as colorlessprisms. m.p. 121°-122° C.

Elemental analysis, for C₁₆ H₂₂ N₂ O₃ : Calcd.: C, 66.18; H, 7.64; N,9.65. Found: C, 66.46; H, 7.68; N, 9.63.

IR spectrum ν_(max) ^(nujol) cm⁻¹ : 1735, 1665 (C═0).

EXAMPLE 29

A mixture of 1.75 g of tert-butyl3-amino-2-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-1-acetate and 1.1 g ofethyl 6-(1-benzyloxycarbonyl-4-piperidyl)-2-methanesulfonyloxyhexanoateis heated at 90° C. for 24 hours. After cooling, the reaction solutionis diluted with 200 ml of ethyl acetate, and the resulting solution iswashed with 30 ml of 5% aqueous phosphoric acid and water, successively,and dried over anhydrous magnesium sulfate. After the solvent isdistilled off under reduced pressure, the residue is separated andpurified by silica gel colum chromatography (hexane:ethyl acetate=2:1),whereby the first fraction yields 0.8 g of tert-butyl3(RS)-[5-(1-benzyloxycarbonyl-4-piperidyl)-1(SR)-ethoxycarbonylpentyl]amino-2,3,4,5-tetrahydro-1H-1-benzazepine-1-acetateas a colorless oil.

IR spectrum ν_(max) ^(neat) cm⁻¹ : 3310 (NH): 1730, 1690, 1665 (C═O).

Mass spectrum (m/e): 649 (M⁺).

From the subsequent fraction, 0.7 g of tert-butyl3-(RS)-[5-(1-benzyloxycarbonyl-4-piperidyl)-1(RS)-ethoxycarbonylpentyl]amino-2-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-1-acetateis obtained as a colorless oil.

IR spectrum ν_(max) ^(neat) cm⁻¹ : 3320(NH); 1730, 1690, 1660(C═0).

Mass spectrum (m/e): 649(M⁺).

EXAMPLE 30

In 2 ml of acetic acid is dissolved 0.8 g of tert-butyl3-(RS)-[5-(1-benzyloxycarbonyl-4-piperidyl)-1(SR)-ethoxycarbonylpentyl]amino-2-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-1-acetate,and 2 ml of 30% aqueous hydrogen bromide-acetic acid solution is addedto the solution, followed by standing at room temperature for 2 hours.The reaction solution is diluted with 200 ml of ethyl ether, and afterthe mixture is allowed to stand, the supernatant layer is removed bydecantation. The precipitate is rinsed with 100 ml of ethyl ether anddried to give3(RS)-[5-(4-piperidyl)-1-(SR)-ethoxycarbonylpentyl]amino-2-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-1-aceticacid.hydrobromide. This product is dissolved in 20 ml of 1N aqueoussodium hydroxide and the solution is allowed to stand at roomtemperature for 1 hour, acidified with 2 ml of acetic acid and purifiedby XAD-2 column chromatography (methanol:water=1:1). The effluent isconcentrated under reduced pressure, and the crystals, which separateout, are rinsed with 50 ml of acetone and collected by filtration togive 0.33 g of3(RS)-[5-(4-piperidyl)-1(SR)-carboxypentyl]amino-2-oxo-2,3,4,5-tetrahydro-1-H-benzazepine-1-aceticacid as colorless prisms. m.p. 250°-260° C. (decomp.).

Elemental analysis, for C₂₃ H₃₃ N₃ O₅.H₂ O: Calcd.: C, 61.45; H, 7.85;N, 9.35. Found: C, 61.50; H, 7.55; N, 9.26.

SIMS spectrum (m/e): 432(MH⁺).

IR spectrum ν_(max) ^(nujol) cm⁻¹ : 1660(C═0).

EXAMPLE 31

In 2 ml of acetic acid is dissolved 0.7 g of tert-butyl3(RS)-[5-(1-benzyloxycarbonyl-4-piperidyl)-1(RS)-ethoxycarbonylpentyl]amino-2-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-1-acetate,and 2 ml of 30% hydrogen bromide-acetic acid solution is added to thesolution, followed by standing at room temperature for 2 hours. Thereaction solution is diluted with 100 ml of ethyl ether, and after themixture is allowed to stand, the supernatant layer is removed bydecantation. The precipitate is rinsed with 50 ml of ethyl ether anddried to give3(RS)-[5-(4-piperidyl)-1(RS)-ethoxycarbonylpentyl]amino-2-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-1-aceticacid.hydrobromide. This product is dissolved in 20 ml of 1N aqueoussodium hydroxide, and the solution is allowed to stand at roomtemperature for 1 hour, made acidic with 2 ml of acetic acid andpurified by XAD-2 column chromatography (methanol:water=1:1). Theeffluent is concentrated under reduced pressure, and the crystals, whichseparate out, are rinsed with 50 ml of acetone and collected byfiltration to give 0.22 g of3(RS)-[5-(4-piperidyl)-1(RS)-carboxypentyl]amino-2-oxo-2,3,4,5-tetrahydro-1H-benzazepine-1-aceticacid as colorless prisms. m.p. 240°-260° C. (decomp.).

Elemental analysis, for C₂₃ H₃₃ N₃ O₅.H₂ O: Calcd.: C, 61.45; H, 7.85;N, 9.35. Found: C, 61.34; H, 7.50; N, 9.36.

SIMS spectrum (m/e): 432(MH⁺).

IR spectrum ν_(max) ^(nujol) cm⁻¹ : 1670(C═0).

EXAMPLE 32

In 10 ml of N,N-dimethylformamide are dissolved 0.56 g of benzyl(S,S,S)-2-azabicyclo[3,3,0]octane-3-carboxylate. hydrochloride and 0.5 gofN-[(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanine.hydrochloride,and 0.3 g of triethylamine is added to the solution under ice-coolingwith stirring, followed by addition of 0.5 ml of diethylphosphorocyanidate. After stirring for 30 minutes, there is added to themixture 0.1 g of triethylamine, followed by stirring for 30 minutes andat room temperature for 1 hour. The reaction mixture is diluted with 100ml of water and extracted with 100 ml of ethyl acetate. The extract iswashed with 5% aqueous phosphoric acid and water, successively, anddried over anhydrous magnesium sulfate. The solvent is distilled offunder reduced pressure, and the residue is purified by silica gel columnchromatography (hexane:acetone=3:1) to give 0.26 g of benzyl(S,S,S)-2-[N-[(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-2-azabicyclo[3,3,0]octane-3-carboxylateas a colorless oil.

IR spectrum ν_(max) ^(neat) cm⁻¹ : 1740, 1690, 1640(C═0).

Mass spectrum (m/e): 675(M⁺).

EXAMPLE 33

In 50 ml of ethanol is dissolved 0.26 g of benzyl(S,S,S)-2-[N-[(S)-5-(1-benzyloxycarbonyl-4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-2-azabicyclo[3,3,0]octane-3-carboxylate,and a catalytic reduction is carried out at ambient temperature andunder atmospheric pressure using 0.2 g of 10% palladium-carbon (50% wet)as a catalyst. After the reaction is allowed to proceed for 4 hours, thecatalyst is filtered off, and the filtrate is concentrated under reducedpressure to give(S,S,S)-2-[N-[(S)-5-(4-piperidyl)-1-ethoxycarbonylpentyl]-L-alanyl]-2-azabicyclo[3,3,0]octane-3-carboxylicacid as a colorless oil. This product is dissolved in 5 ml of 1N aqueoussodium hydroxide, and the solution is allowed to stand at roomtemperature for 1 hour, made weakly acidic with 1 ml of acetic acid andpurified by XAD-2 column chromatoraphy (0.15M aqueous ammonia-5%acetonitrile). The effluent is concentrated under reduced pressure, andthe concentrate is lyophilized to give 0.15 g of(S,S,S)-2-[N-[(S)-5-(4-piperidyl)-1-carboxypentyl]-L-alanyl]-2-azabicyclo[3,3,0]octane-3-carboxylicacid as a colorless powder.

Elemental analysis, for C₂₂ H₃₇ N₃ O₅.3/2H₂ O: Calcd.: C, 58.65; H,8.95; N, 9.33. Found: C, 58.46; H, 8.80; N, 9.35.

SIMS spectrum (m/e): 424(MH⁺).

EXAMPLE 34

In 100 ml of water is dissolved 20 g of succharose, and 10 g of Baker'syeast (Oriental Dry Yeast) is added to the solution, followed bystirring at 30° C. for 10 minutes. To the mixture is added a solution of1 g of ethyl 6-(1-benzyloxycarbonyl-4-piperidyl)-2-oxohexanoate in 3 mlof ethanol, and the resulting mixture is stirred for 46 hours. To themixture is added 150 ml of ethyl acetate and the insoluble material isremoved by filtration. The ethyl acetate layer is separated and theaqueous layer is further extracted with ethyl acetate. The ethyl acetatelayers obtained are combined, dried (MgSO₄) and concentrated underreduced pressure. The residue is purified by silicagel columnchromatography to give 0.34 g of ethyl(R)-6-(1-benzyloxycarbonyl-4-piperidyl)-2-hydroxyhexanoate as acolorless oil. The product is converted to its ester of(-)-α-methoxy-α-trifluoromethylphenylacetic acid and subjected toquantitative analysis by high performance liquid chromatography (HPLC).The result is that the enantiomeric excess (% e.e.) is 54%.

EXAMPLE 35 to 37

The α-oxoesters shown in the following Table are reduced by Baker'syeast in the same manner as described in Example 34 to give thecorresponding (R)-α-hydroxyesters, respectively.

    __________________________________________________________________________    Example No.                                                                          Starting Material  Product             Yield % (%                      __________________________________________________________________________                                                  e.e.)                           35                                                                                    ##STR161##                                                                                       ##STR162##         52 (37)                         36                                                                                    ##STR163##                                                                                       ##STR164##         43 (32)                         37                                                                                    ##STR165##                                                                                       ##STR166##         31 (30)                         __________________________________________________________________________

EXAMPLE 38

To a solution of 2.3 ml of oxalyl chloride in 40 ml of methylenechloride cooled at -65° C. is added a solution of 4.45 g ofdimethylsulfoxide in 20 ml of methylene chloride over a period of 10minutes, and the mixture is stirred at -60° C. for 10 minutes. To themixture is added a solution of 5 g of ethyl6-(1-benzyloxycarbonyl-4-piperidyl)-2-hydroxyhexanoate in 50 ml ofmethylene chloride over a period of 10 minutes, and the resultingmixture is stirred at -60° C. for 20 minutes. To the mixture is added10.3 g of diethylisopropylamine over a period of 10 minutes, and thetemperature is raised from -60° C. up to -30° C. To the mixture is added80 ml of 1N hydrochloric acid, and the mixture is stirred at roomtemperature. The methylene chloride layer is separated, washed withwater, dried and concentrated under reduced pressure. The residue ispurified by silicagel column chromatography (hexane: ethyl acetate=4:1to 2:1), to give 2.6 g of ethyl6-(1-benzyloxycarbonyl-4-piperidyl)-2-oxohexanoate as an oil.

EXAMPLES 39 to 41

The α-hydroxyesters shown in the following Table are oxidized in thesame manner as described in Example 38 to give the correspondingα-oxoesters, respectively.

    __________________________________________________________________________    Example                                                                            Starting                                                                 No.  Material          Product (Yield %)                                      __________________________________________________________________________    39                                                                                  ##STR167##                                                                                      ##STR168##                                            40                                                                                  ##STR169##                                                                                      ##STR170##                                            41                                                                                  ##STR171##                                                                                      ##STR172##                                            __________________________________________________________________________

EXAMPLE 42

In 0.7 ml of pyridine is dissolved 0.18 g of ethyl(R)-6-(1-benzyloxycarbonyl-4-piperidyl)-2-hydroxyhaxanoate obtained inExample 34, and 0.11 g of methanesulfonyl chloride is added to themixture under ice-cooling with stirring. After stirring for 2 hours, 0.1ml of water is added to the mixture and the resulting mixture is stirredfor 20 minutes. To the mixture are added 30 ml of water, 5 ml of ethylacetate and 5 ml of hexane, and the organic layer is separated, washedwith water, 1N hydrochloric acid, water, aqueous sodium bicarbonate andwater, successively, dried over anhydrous magnesium sulfate andconcentrated under reduced pressure to give 0.2 g of ethyl(R)-(1-benzyloxycarbonyl-4-piperidyl)-2-methanesulfonyloxyhexanoate.

EXAMPLE 43

A mixture of 0.32 g of tert-butyl(RS)-3-amino-2-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-1-acetate and 0.2g of ethyl(R)-(1-benzyloxycarbonyl-4-piperidyl)-2-methanesulfonyloxyhexanoate isheated at 90° C. for 30 minutes. After cooled, the mixture is separatedand purified by silicagel column chromatography (hexane: ethylacetate=2:1) to give 0.14 g of tert-butyl3(R)-[5-(1-benzyloxycarbonyl-4-piperidyl)-1(S)-ethoxycarbonylpentyl]amino-2-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-1-acetateas colorless oil from the first fraction.

IR spectrum ν_(max) ^(neat) cm⁻¹ : 3310(NH); 1730, 1690, 1665 (C═0).

Mass spectrum (m/e): 649 (M⁺).

From the second faraction, 0.12 g of tert-butyl3(S)-[5-(1-benzyloxycarbonyl-4-piperidyl)-1(S)-ethoxycarbonylpentyl]amino-2-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-1-acetateis obtained as colorless oil.

IR spectrum ν_(max) ^(neat) cm⁻¹ : 3320(NH); 1730, 1690, 1660 C═0).

Mass spectrum (m/e): 649 (M⁺).

EXAMPLE 44

3(S)-[5-(1-Benzyloxycarbonyl-4-piperidyl)-1(S)-ethoxycarbonylpentyl]amino-2-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-1-acetateis treated with hydrogen bromide, subjected to alkaline hydrolysis andpurified by XAD-2 column chromatography in the same manner as describedin Example 30 to give 0.03 g of3(S)-[5-(4-piperidyl)-1(S)-carboxypentyl]amino-2-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine-1-aceticacid as a colorless powder.

EXPERIMENTAL EXAMPLE 1

Effect of Compounds of The Present Invention against HypertensiveActivity of Angiotensin I

Experimental Method

There were used male rats (Sprague-Dawley) weighing 300 to 400 g whichwere bred under free access to feed and water. The rats wereanesthetized by intraperitoneal injection of pentobarbital sodium (50mg/kg) on the day before the experiment, whereupon polyethylene tubeswere inserted into the femoral artery for measurement of blood pressureand the femoral vein for injection of angiotensin I and II, and thetubes were fixed.

On the day of experiment, the average blood pressure in the controlphase was measured by use of an electric hemodynamometer(MPU-0.5-290-O-III model, manufactured by NEC-Sanei of Japan) andrecorded with a polygraph (365 model manufactured by NEC-Sanei or RM-45model manufactured by Nippon Kohden of Japane), and thereafterangiotensin I and then angiotensin II were injected through the femoralvein in a dose of 300 ng/kg and 100 ng/kg, respectively, to determinetheir hypertensive activities. Then, the compound of this invention wasadministered intravenously as a solution in physiological saline, andangiotensin I and II were injected repeatedly 5, 10, 30, 60, 90 and 120minutes after the administration, respectively, to trace thehypertensive reactions. In calculating the rate of inhibition againstthe hypertensive activity of angiotensin I, the rate of inhibition wascorrected based on the variation with time in the hypertensive reactionby angiotensin II.

Experimental Results

The experimental results with compounds of this invention are as shownin Table 6.

                                      TABLE 6                                     __________________________________________________________________________                     Rate (%) of inhibition against hypertensive                  Test Comp'd.                                                                          Amount (μg/kg)                                                                      activity of angiotensin I in relation to time                No. of Example                                                                        administered i.v.                                                                      5 min.                                                                            10 min.                                                                           30 min.                                                                           60 min.                                                                           90 min.                                                                           120 min.                                 __________________________________________________________________________     3      300      100  99 100 100 100 98                                        6      300       77  84  86  86  80 61                                       20      300      100 100 100 100 100 92                                       23      600       95  98 100  96  92 94                                       31      600      100 100 100  92  83 90                                       33      300      100 100  91  91  91 91                                       __________________________________________________________________________

What is claimed is:
 1. A compound of the formula ##STR173## whereinR^(4') is lower alkyl; R¹ is hydrogen, lower alkyl or phenyl-loweralkyl; R² is hydrogen, lower alkyl, phenyl-lower alkyl, lower alkanoyl,benzoyl, phenyl-lower alkoxycarbonyl or lower alkoxycarbonyl; and X isC₁₋₇ alkylene; or a pharmaceutically acceptable salt thereof.
 2. Acompound according to claim 1, wherein R¹ is hydrogen or lower alkyl. 3.A compound according to claim 1, wherein R¹ is hydrogen.
 4. A compoundaccording to claim 1, wherein R² is hydrogen.
 5. A compound according toclaim 1, wherein X is trimethylene, tetramethylene or pentamethylene. 6.A compound according to claim 1, wherein X is tetramethylene.
 7. Acompound according to claim 1, which isN-[N-[(S)-1-carboxy-5-(4-piperidyl)pentyl]-L-alanyl]-N-(indan-2-yl)glycine8. A pharmaceutical composition suitable for prevention or treatment ofhypertension which comprises, as an active ingredient, an effectiveantihypertensive amount of a compound as claimed in claim 1 or apharmaceutically acceptable salt thereof, and a pharmaceuticallyacceptable carrier, excipient or diluent therefor.
 9. A method forprevention or treatment of hypertension in a mammal, which comprisesadministering to said mammal an effective antihypertensive amount of acompound as claimed in claim 1 or a pharmaceutically acceptable saltthereof.